2015 Indmar Monsoon 409SS THERMOSTAT LOCATION HELP

[2011vlx]

Can anyone help lead me to the location of the thermostat on a 2015 Indmar Monsoon 409SS and its difficulty in changing.  Seems like it should be an easy job if can get to it.  I have a picture of where I think it is but not sure how to post it here?

[PNWoke]

I can’t tell you exactly where it is but I can confirm that it’s pretty easy to fix.  Local Bu shop found mine was intermittently failing on my preseason check this year.  I was only charged for the minimum 30 mins of tech time, it likely was a 10 minute job.  

[csleaver]

The thermostat is located very low on the front bank 2 side of the engine, which is on the port side of the boat.  You will see a large seawater tube and hoses that connect the rectangular thermostat adaptor housing to the the raw water pump.

[2011vlx]

I would love to post a pic here to make sure I'm thinking it's the correct thing but I'm not sure how to do that?  Csleaver any chance you can post a pick or lead me to a YouTube video showing it and maybe changing it.  I believe it won't be a hard job I just don't want to take apart something I shouldn't.  

[csleaver]

25 minutes ago, 2011vlx said:

Csleaver any chance you can post a pick or lead me to a YouTube video showing it and maybe changing it.

It may be hard to find a video or pictures of a thermostat replacement procedure for that engine online, because it is not a very common repair.  Just curious, why does yours need replacement? 

Front of L96 engine with the T-stat housing on the left.

 

[csleaver]

You can post pictures by becomming a member, or by using a link to a Dropbox photo or similar media hosting service.

[2011vlx]

Thanks Csleaver, when running my boat it's running hotter than normal, especially at idle.  I have replaced the impeller and when doing so the old one wasn't in bad shape.  I have also pulled a few hoses off, one where the intake water goes into the transmission and another one where it goes into the small hoses/pipes by one of the exhausts.  I was thinking maybe there would be debri in there etc.... but everything in those to areas was clear.  So my next best guess is the thermostat.  I will try and post a picture but in the one you posted with the green arrows, those arrows it appears all point to different hoses, the second arrow top to bottom on the left of the picture is the thermostat in that metal rectangle housing that hose turns 90 degrees into?

[csleaver]

You may be having a problem with the cooling system air drain.  There is a small rubber hose connected to a small air drain pipe on the top of the engine intake manifold near the front port side of the engine.  The hose goes from the air drain pipe to a through-hull fitting located just above the port exhaust outlet at the transom.  If the hose, air drain pipe, or transom fitting becomes blocked, then air gets trapped in the cooling passages and often causes the engine to over heat at idle speed.  Once the engine is run above 2000 RPM the air is often purged and will return to normal temperatures, but at idle speed the engine can over heat if the purge system is blocked.  You should be able to see a stream of water coming out of the small metal through-hull fitting located just above the port exhaust tip when you are standing behind the boat and running the engine out of the water using a hull motor flush.  If you don't see the stream of water, then the air purge is probably blocked. 

The thermostat adaptor housing is the rectangular piece on the left of the photo with all the hoses and 90 degree plastic fittings connected to it.  The green arrows in the picture I found weren't drawn by me, they were already there for another purpose. 

Edited April 28 by csleaver

[2011vlx]

Thanks Csleaver, I really appreciate your help.  I will take a look this evening!

[2011vlx]

Csleaver, I know this is the wrong motor, it's an Indmar 350 but would this be the hose I am looking for?  Item 149 in this picture https://www.indmar.com.au/engineschematics/chevy/pre-2014/monsoon-5-7-assault-340hp-345hp-350hp/upper-intake-assembly.html

 

Edited April 29 by 2011vlx
typo

[JasonK]

Item 149 Is the PCV breather hose. No thermostat hose in your pic.

[justgary]

Just for clarity, the LS thermostat housing is at the far left side of the circulation pump casting:

It is very common around here for mud daubers to block small holes like the "pee tube" on a wide variety of boat engines.  It might be worth the trouble to find the transom outlet that @csleaver mentioned and inspect it for mud or other evidence of bugs.  A wire is the tool of choice to break up the mud to get a path for the water to flow again.  Another option might be to find the other end at the intake manifold and pulse it with a bit of compressed air to make sure it is clear.

[2011vlx]

JustGary, appreciate it!  On my 409SS that silver hosing is not there, mine is a bit older a 2015 model so I'm assuming that is a newer motor in your pic.  Good chance it's a mud daubers problem as I do find that in my speakers and board rack holes etc.... all advice is appreciated, thank you!

[csleaver]

Here is another post about the air bleed hose.

 

[2011vlx]

Great, appreciate it Csleaver! 

 

[justgary]

4 hours ago, 2011vlx said:

On my 409SS that silver hosing is not there, mine is a bit older a 2015 model so I'm assuming that is a newer motor in your pic.

My photo is from an automotive engine.  You asked where the housing is, and it was very easy to see in that photo.  It was a bit hard to see in the black-on-black with black hoses everywhere in the other photo.

[2011vlx]

 

hey guys @csleaver & @justgaryHey guys, so I ran the boat out of the water with a garden hose, I have no water coming out of that "pee hole" that I didn't know existed.  I let it get to normal operating temp.  Should it be coming out under idle or under idle speed on a hose or only once you give it some RPM'S which I normally wouldn't do out of the water?  I was able to get the hose disconnected at the passthrough, and I was able to run a piece of weed wacker string all the way to where it would enter the motor and it met no resistance or clogging.  However, running the boat out of the water on a house no water comes out of that pee hole, not even a drip and I let the engine go to 10 degrees above normal operating temp before shutting it down.  I'm feeling like thermostat unless you have any other suggestions.  I truly appreciate your guys help!

Edited April 29 by 2011vlx
additional information

[csleaver]

Water should be coming out of the air bleed fitting at all engine speeds, from idle up to wide open throttle.  If there is not a constant stream of water at the bleed fitting after running the engine for more than 60 seconds, then there is a blockage somewhere in the air bleed system.  You may need to remove and clean the crossover bleed tube and intake manifold holes where it mounts, or there could be a blockage in the hose.

This is a common issue with GM GenIV engines which use only raw seawater in the cooling system due to the high amount of corrosion and debris which occurs in that type of cooling system.

[csleaver]

If you are still determined to replace the thermostat, it is Indmar PN: 986115 - THERMOSTAT 160 Deg GEN4 6.0L

[2011vlx]

man, @csleaver that is really helpful.  I"m still open to other ideas if you think I should still be looking elsewhere.  I am concerned no water is coming out of the "pee hole" when running on the hose???  I will try to dig further into the potential air bleed issue, I really appreciate your guidance! 

[2011vlx]

Thanks @csleaver I'm going to take a look at removing/cleaning the "crossover bleed tube & intake manifold holes" you mentioned.  If you have easy access to a photo and could share that would be amazing, just want to make sure I'm looking at the right tubes etc.... 

[2011vlx]

Man I am so pumped @csleaver you nailed it!  I figured out what the crossover bleed tube (thin metal pipe) was, took it off and it was 50-60% clogged in 1 small area with rust just like you said.   I cleaned it out and boat is running like normal!  Can't thank you enough, saved me 3 hours of towing it to a dealer and probably being without the boat for weeks plus the cost!  Thank you again sir!

Edited May 1 by 2011vlx

[201522vlx]

@2011vlx do you mind sending a photo of the crossover bleed tube. I’m running into the same problem with my 2015 vlx with the 409.